The present application relates to fluid filters, and particularly to fluid filters that are subjected to impinging fluid flow on the filter medium. The invention is broadly applicable and can be used in hydraulic, fuel and air filter applications.
Fluid filters are commonly used to prevent contaminants, especially particles, in the fluid from passing through the filter to downstream components. Fluid filters have many different constructions, but often include a support material in addition to the actual filter media. In addition, the filter media is usually part of a filter cartridge. The cartridge either acts as, or is designed to fit within, a chamber. The chamber and filter media are configured such that fluid entering the chamber must pass through the filter media before it exits the chamber.
In one application, fluid enters the chamber from a pump which increases the fluid's pressure for downstream applications. The filter cartridge is generally cylindrical. After leaving the pump, fluid flows into the filter chamber and enters from the outside of the filter, through the media, into a central chamber, which is connected to the outlet of the chamber. It was discovered that the cartridge was failing during use, and the area of failure was the end caps of the cartridge that connected to the filter chamber. It was believed that the fluid from the pump was impinging on the filter cartridge in a tangential manner, causing the cartridge to spin on its mountings. The spinning action caused wear on the fittings on the end caps of the filter, causing them to fail. Thus the fittings were strengthened, and it was decided to add features to the cartridge that would prevent it from spinning inside the chamber.
This fix prevented the fittings on the end caps from wearing and failing. However, it was later discovered that the filter media was failing, thereby allowing contaminants to pass-through the filter. Since the filter media had not been altered when the cartridge was changed to add the anti-rotation feature, it was unclear why the filter media was found to be failing. Several different approaches were considered to solve the problem, including using stainless steel wire to help support the filter media, and an outer guard tube with many holes through it. Also, changes were considered for the filtration media and pleat design. However, these initial approaches did not seem to solve the problem. Thus, there is a need for a filter cartridge that can be used in the chamber that will adequately filter the fluid without the media failing. Also, the cost and weight of the cartridge need to be kept at a minimum.